Appendix D: Differences from Other Processors

If you know another XPath, XQuery or XSLT processor, most of what you know applies to sxml unchanged: the languages are standards, and sxml follows them closely. These are the differences you are most likely to notice.

The 4.0 languages

sxml implements the 4.0 versions of XPath, XQuery and XSLT, so you can use their new syntax everywhere: { } map constructors without the map keyword, fn { } and fn($x) { } inline functions, string templates in backticks, otherwise, =!>, for member, records, while clauses in FLWOR expressions, default parameter values and keyword arguments, transform with, and the new functions such as sort-by, highest, partition, parse-csv and parse-html.

Older code keeps working. XPath 3.1 and XQuery 3.1 expressions are 4.0 expressions, and XSLT 1.0, 2.0 and 3.0 stylesheets run with the behaviour their version attribute asks for, XPath 1.0 compatibility mode included. The 4.0 specifications are still drafts, and where a draft changes, sxml follows the newer text.

No network, few files

The sxml library reads only what its resolver gives it, and the sxml command's resolver reads only local files. doc("https://...") is not fetched. External DTDs and entities are not read unless you ask for them, EXPath File exists only with --allow-file-access, and fn:put writes only with --allow-put. Processors that read URLs and files by default will behave differently here on purpose.

XInclude is processed only when a call asks for it: fn:doc and fn:parse-xml with the options xinclude and trust-external both true. xpointer attributes are not supported; an include that has one takes its xi:fallback.

Output

The sxml xpath command writes results by the adaptive output method, which shows types: strings in quotes, doubles in exponent notation, and other atomic values as constructor calls, such as xs:date("2026-10-20"). Choose --method=text or another method when you want plain output.

Error messages

Error codes are those of the specifications, so try/catch and xsl:catch code that tests them carries over. The descriptions are sxml's own, and name the section of the specification that decides the error.

Extensions

sxml has no extension functions of its own beyond EXPath Binary and EXPath File and EXSLT Common in XSLT 1.0 stylesheets, and it runs no code written in other languages from a query. A C program that embeds sxml can pass its own functions to a query as function items.

Limits

Every evaluation runs under limits on the work it does, the depth of its calls and the memory it uses, which a program sets in the processor's configuration. The defaults are generous (a hundred million evaluation steps, a million nested calls), and they keep an accidental infinite loop from running forever. sxml never uses the C stack for deep nesting, so deeply nested documents and deeply recursive functions are bounded only by these limits and by memory.